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inputing a text file into an array

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andyg55

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inputing a text file into an array

Jan 26th, 2008

Hi,

I'm trying to create a 2d array that will fill itself up with numbers i have in a text file.

My text file looks like this:

1 5 4
2 6 3
3 9 4
4 1 8
5 2 2

So, I want to create an array with 5 rows and 3 columns that will print this exact output to the screen.

Could anybody help me with the code please?

Thank you

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twomers

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Re: inputing a text file into an array

Jan 26th, 2008

>> Could anybody help me with the code please?
Not unless you show some work.
But it's not that hard. There are two problems to overcome -- 1) filling the array 2) reading values from a file. Once you have those two done there's really no problem. Show attempts on both.

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Re: inputing a text file into an array

-1

Jan 26th, 2008

 Help with Code Tags 
 c++ Syntax (Toggle Plain Text) 
#include <iostream.h>
#include <fstream.h>
 
int main()
{
/* open the file to read from in this case being your text file*/
char chars[50];
char newline = '\n'; // for the get line function's 3rd argument .. acts as a terminating delimeter.
 
ifstream in("c:\\documents and settings\\your profile name\\desktop\\theNameOftheTXTfile.txt");
 
while(! in.eof())
{
in.getline(chars,50,newline);
cout<<chars<< endl;
};
system("pause"); // I use DEV as im a hobby 
                         //programmer.
return 0;
};
#include <iostream.h>
#include <fstream.h>

int main()
{
/* open the file to read from in this case being your text file*/
char chars[50];
char newline = '\n'; // for the get line function's 3rd argument .. acts as a terminating delimeter.

ifstream in("c:\\documents and settings\\your profile name\\desktop\\theNameOftheTXTfile.txt");

while(! in.eof())
{
in.getline(chars,50,newline);
cout<<chars<< endl;
};
system("pause"); // I use DEV as im a hobby 
                         //programmer.
return 0;
};

I didnt compile this code.. should work, if not post the error, and I will get back to this post later.

NOTE: This reads the text in as characters, so although they are numbers in the note pad, they will be read in as characters. **some people like to write stuff to text files, and read from text files without having to use the isstream class if your doing most of your work on a windows platform.

Last edited by Ancient Dragon; Jan 26th, 2008 at 9:33 pm. Reason: add code tags

Name: Cody Oebel
Place : San Antonio , TX.

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Re: inputing a text file into an array

Jan 26th, 2008

Cody: if you want to post code, that is ok, but please

Use code tags [code=c++] /* code goes here */ [/code]
Don't use ancient header files with .h extension
Don't use eof() as you did in line 12 because it doesn't work like that

>> This reads the text in as characters
Why? it could read into integer variables just as easy. By reading in as strings the strings have to be converted into ints before they can be used. That just extra unnecessary work.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.

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andyg55

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Re: inputing a text file into an array

Jan 27th, 2008

Ok, sorry for not showing you what i've got.

I'm looking for something really simple, all I want to do is fill an array/matrix with my infile!!

In my example, there were only a few rows of information, but this needs to be able to be replaced with something, say, of 100 row of information. Thus, the program needs to be quite general.

I thought maybe zero the array first?

At the moment I have this code for the array...

k = 0;

for (i=1; i<101; i++)

{

for (j=1; j<3; j++)
{
matrix[i][0] = i;
matrix[i][1] = k;
matrix[i][2] = k; }

printf("%d", matrix[i][0]);
printf("\t%d", matrix[i][1],k);
printf("\t%d", matrix[i][2],k);
printf("\n");}

}

And as for uploading the input file from notepad, i believe i should use...

inFile.open("input.txt");
if (!inFile) {
cout << "Unable to open file";
exit(1); // terminate with error
}

Am I on the right tracks? Oh, and that code already posted din't work at all

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Re: inputing a text file into an array

Jan 27th, 2008

You don't need to zero out the array. You already know the size (5 x 3), so declare it that size:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int matrix[5][3];
int matrix[5][3];

i would just read it in like this:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for (int i = 0; i < 5; i++)
{
    for (j = 0; j < 3; j++)
    {
        inFile >> matrix[i][j];
        // display matrix[i][j]
    }
}
for (int i = 0; i < 5; i++)
{
    for (j = 0; j < 3; j++)
    {
        inFile >> matrix[i][j];
        // display matrix[i][j]
    }
}

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Re: inputing a text file into an array

Jan 27th, 2008

•

Originally Posted by VernonDozier

You don't need to zero out the array. You already know the size (5 x 3), so declare it that size:

Nope...

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Originally Posted by andyg55

In my example, there were only a few rows of information, but this needs to be able to be replaced with something, say, of 100 row of information. Thus, the program needs to be quite general.

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Re: inputing a text file into an array

Jan 27th, 2008

Yeah, sadly it needs to be replaced with a file of unknown size

I've been told it won't be over 100 rows though

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Re: inputing a text file into an array

Jan 27th, 2008

Missed that part of the problem. Thanks.

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Re: inputing a text file into an array

#10

Jan 27th, 2008

So here is the basic program I have. All this does is read a .txt file and produce a 100x3 array that is zero'd. What alterations/additions do I make to the code to import the .txt file into the array? Thanks in advance!!

 Help with Code Tags 
 c++ Syntax (Toggle Plain Text) 
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>
 
int k,i,j;
int matrix[101][5];
 
main () {
 
  ifstream inFile;
  inFile.open("input.txt");
 
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error
    }
  inFile.close();
 
  k = 0;
 
  for (i=1; i<101; i++)
 
  {
 
  for (j=1; j<3; j++)
  {  
     matrix[i][0] = k;
     matrix[i][1] = k;
     matrix[i][2] = k; }
 
  printf("%d", matrix[i][0]);
  printf("\t%d", matrix[i][1],k);
  printf("\t%d", matrix[i][2],k);
  printf("\n");}
 
}
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>

int k,i,j;
int matrix[101][5];

main () {
  
  ifstream inFile;
  inFile.open("input.txt");
  
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error
    }
  inFile.close();
    
  k = 0;

  for (i=1; i<101; i++)
  
  {
    
  for (j=1; j<3; j++)
  {  
     matrix[i][0] = k;
     matrix[i][1] = k;
     matrix[i][2] = k; }

  printf("%d", matrix[i][0]);
  printf("\t%d", matrix[i][1],k);
  printf("\t%d", matrix[i][2],k);
  printf("\n");}

}